Post 52 –by Gautam Shah


(Lecture series: Space Perception -Article-VII of 15)

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‘Turn around a street corner and the smell changes because a new orientation has different visual and aural scale and airs movement. In many instances a different set of culture’ suggests itself. Cities offer “a rich melange of olfactory and other sensations”. Smell is an experience of living, and the nature, so represents a terrain-based location. Smell is an intangible property of tangible heritage.

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A city has neighbourhoods, each with distinctive smell. The smell has cultural significance for a place, but has no history to denote. The distinction is ethnological through cultural, religious and other practices. Odours have strong compartmentalizing factor for a society. We easily sense the ethnic groups with a different diet, but to distinguish members of our own tribe, we have to rely on other means such as visual (body) and aural (speech-diction) features. (After- Urban Smell-scapes: Understanding and Designing City Smell Environments By Victoria Henshaw)

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5th C BC Sophocles describes Thebes as ‘heavy with mingled burden of sounds and smells, of groans, hymns and incense.

Nero’s Rome was full of stench of refuse rotting by the wayside, the piercing fragrance of burning myrrh from the temples, a heavy aroma of foods being cooked in the street, sweet seductive scents of flowering gardens, the mal-odour of rotting fish, sharp smell of urine from public latrines, and incense trail of passing procession -Aroma: The Cultural History of Smell.

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On a typical day some 10,000 people would be present at Versailles estate. But there were hardly any toilets, not even for the aristocrats. And everyone, without exception to their position would occasionally ease themselves in courtyards, interior corners or under the stairs. Visitors complained about the awful stench that was omnipresent everywhere. Chamber pots overflowed and moisture seeped into the structure. It was visually a splendid palace, but a stinkiest one. Louis XIV put a new rule in place according to which the hallways were to be cleansed once every week. Orange trees’ cuttings were placed in vases to mask the smell.

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The City of Paris had terrible sanitary conditions. There was no system for management of solid wastes and night soil waste. Servants emptied the pots out of the windows. In a city where water pipes were laid to enliven fountains, but not carry the sewage. Solid waste of repairs or demolition of buildings was simply spread out on the streets or public lands. Cities’ streets were full of ground dirt of debris, mixed with night soil and blood from slaughterhouses. Dirt, dung, food, and filth mix rose to ankle-deep levels. At places ground floors were buried and became cellar floors. It soiled the clothes so badly that no soap could remove the stain or stink of it. Kings dictate to clean up the city, asked the commissioners to carry away the debris, and dump it in the river Seine. Things were no different across towns across the world and till 1900s.

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Place making has emerged as the central theme in Urban Design. It is ‘aimed at rediscovering, enhancing, protecting or creating locally significant place related meanings’. —Urban Smell scapes: Understanding and Designing City Smell Environments By Victoria Henshaw.

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Our urban smell environment once comprised of open sewers, open heaps of garbage, animal excreta, meat-fish shops, slaughterhouses and factories near residential areas, diesel vehicles and exotic foods. The smells were intimately linked with the density of population, social and economic conditions of the community, distribution and proportion of open spaces and orientation and patterns of street layout and climate of the place. For these reasons, it is common to see connections drawn between unpleasant smells (the definition of which is also contentious) and poverty and specific ethnicities. Urban geographical isolation of communities through political machinations has the basis in smells and related social and religious prejudices.


The smell-based geography is more of visitors’ perception, local residents are smell habituated. Smell of a place is a unique brand for tourism. Other tangible heritage can be recorded and recreated, but smell of a place is variable and circumstantial, so unless the totality of living and environment are allowed to flourish, the smell will disappear.

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Japanese Ministry for the Environment through a survey listed 100 most important smells of Japan (including ancient woods, sea breeze, sake distilleries and a street lined with bookshops) This was a cultural legacy to be handed down to the children.

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The smell-knowledge of the past is odourless. We used to smell history in museums, but not in open to sky archeological sites. Museums, once allowed the smell of books, artefacts, because these were stored in open cases. It was realized that such smells emanate from the processes of decay, and so exhibits are now sealed in vacuum or gas.

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In built spaces, we were, once able to simultaneously experience exterior and interior olfactory environments. For many children of late 20th C the exteriors were for the experience of ‘unused or pristine spaces’. The exteriors are now becoming vastly inter-connected or continuous spaces with controlled environments. New built structures offer some ‘freshness’ of the unused spaces.

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The smell ‘habituation’ and smell personalization are aspects of occupation of interior spaces. New occupants change the interior furnishings and repaint the space to scour the effects of earlier occupation, and imprint it with odours of own lifestyles. The process is very similar to a conscious attempt of visual changes made to domesticate and personalize a home into a distinguished entity.

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Smell is gradually being eliminated from our Urban living, with factory cooked foods, ventilation through tall ducts, air-filtering devices, better environmental controls and planning of public spaces and streets, in consideration of natural air movements, use of non-fossil fuels, preference for neutral odours in all consumer goods.

Space City Day Window Room Living View Modern

Smell neutral space of modern urban setting is not an exclusive process sensorial perception. Cities are losing the local spatial variations through equal architecture and equally bland environment. This is a continuing process. Night darkness of the middle ages towns were removed with street lighting as well as interior illumination through glazed windows and feebly lit architectural lanterns and steeples. Later the city noises of trams, trains and industry of late 19th C were removed. The cluttered city spaces have clean and well-articulated streets and public spaces. Sensorial subduing may regulate the tactility in living.

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Post 51 –by Gautam Shah


(Lecture series: Space Perception -Article-VI of 15)


There are main two facets, each for Smell and Space. Both are real, and also manifest in recollections. For design considerations, visual, audio and tactile experiences can define a space. But smell alone cannot define a space. Smell, like the vision and hearing, is not a space scaling factor. A spatial experience arises from the shape, size and scale of a space, but its smell chiefly emerges from the environment of the space. The source is not part of what we perceive in a smell mechanism. A space through its configuration and openings allows concentration or dilution of smell forming elements. The smell generating elements are of two basic types: materials of space forming and habitation. The built spaces have smells of their own, whether it is an unused relic or inhabited entity.

Incense smoke filled space of The Funeral Procession of Agamemnon ART By Louis-Jean Desprez -

Sense of smell is related to spatial remembrances, but not as a single phenomenon. We recollect it, in association with other things like the visual and audio qualities of space. Once we smell something, the recollection of a particular situation or space is powerful. It is difficult to imagine smell of a place from representations like audio, photograph, video or description.


Our spatial experiences with smells are substantially environmental. An actual space with the interlaced environment lets one to predict or recall comparable ‘smell-conditions’. A lay person, however, cannot separate out the space, environment and its smells. The role of some architectural components typically openings and volume are basic to the living with the smells. Smells change with environmental conditions, like it is more effective in dry and cool, but higher temperatures cause smells to feel more pronounced as it spreads further.

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Intensive engagement and temporal over-exposures to good or bad smells, are traumatic due to insufficiency of breathable air. Smells form dislike for the space-environment and cause loss of comfort, well being, concentration, productivity and appetite. The sense of smell is a basic element for comfort though influenced by experience, expectations, personality and situational factors.

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Smells have a connection to feel good or bad aspect of a space. And this varies with the communities. In confined indoor spaces the concentrations of odours increase many times due to lack of fresh air for dilution. The sense of smell gets fatigued with such intense and continuous exposure. This is beginning of physiological and physiological side-effects. Sense of smell, however, can recover, if the stimulus is removed.

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The smell ‘habituation’ depends on physical conditions and memories of past exposures to similar situations. The sensitivity and ability to perceive smells are unique to each person, but the capacity to discriminate odours, reduce with exposure and age. The threshold before an odour becomes a nuisance, depends on the frequency, concentration, and duration of an odour. Memories of odours are significantly more intense and evocative, than those recalled by the visual or audio cues.


Most memories that pertain to an odour come from the first decade of life, compared to verbal and visual memories which usually come from the 10th to 30th years of life’. ‘Odour-evoked memories are more emotional, associated with stronger feelings of being brought back in time, and have been thought of less often as compared to memories evoked by other cues’. (Willander, Johan & Larsson, Maria. (2006). Smell Your Way Back to Childhood: Autobiographical Odor Memory. Psychonomic bulletin & review. 13. 240-4. 10.3758/BF03193837.)

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Smell is a primal sense. It impacts relationships with people, liking for places, foods, and products. The sense of smell enables pleasure, can subconsciously warn of danger, help locate mates, find food, or detect predators.

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Of the common sensorial perceptions, Olfactory function directly relates to emotion and sense of well being. The emotions are, some universal, others culture specific but mostly associative. The smell is seamless, and if ‘neutral’ in effect, there is no acute need to trace its source. An incense in church, temple or mosque may add devotional fervour, but one infused in commercial and public places, is more subtle, masking with a less emotional content. Smell branding Commercial spaces include offices, trade-booths in exhibitions, fashion-shows, large format retail outlets, hotels, automobile showrooms, metro UG stations, passenger air crafts, etc. Smell branding of such spaces serve many different intentions like: familiarity, reliability, loyalty, memorability, consistent identity, productivity, promote sales, provide sense of well being, inculcate safety-security, thematic alignment, etc.


Today, Hyatt Place’s signature scent can be found in almost 300 hotels across the U.S. The scent is such a proven brand asset that it has been codified as a brand standard that defines the company’s experience and brand personality”. -https://hbr.org/2018/04/inside-the-invisible-but-influential-world-of-scent-branding.

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Studies show that humans can distinguish about one trillion odours. Smells are part of culture and belief systems. In spite of the vast ability to distinguish one smell from the other, it has not been possible to formally define that into some rational classes. Smell, like colour or texture has been difficult to describe characteristics. Colour and Texture are now codified, but sense of smell still evades the definition. We do not have any plausible vocabulary for different smells. We tend to identify the source of smell rather then its class, like eggy, meaty, floral, nutty. Aristotle classified odours in Seven categories: aromatic, fragrant, alliaceous (garlic), ambrosial (musky) hiricinous (goaty), repulsive, and nauseous.

“–there is a geography of places characterized by variety and meaning, and there is place-less geography, a labyrinth of endless similarities. –Ralph 1976-140 “.

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Japanese Government identified 100 locations with ‘good fragrances’, and the list includes: early morning markets, old books stores, grilled sweet-fish of the Gogasegawa river, and Nabu rice crackers of Morioka.


The smell defies codification mainly due to lack of mechanics to measures it. The WHO defines the annoyance threshold for odour nuisance as being at a level where five percent of a specified population experience annoyance for two percent of the time. But this are personal or cultural references.

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English word Perfume literally means ‘to smoke through’ and that relates to fire and warm air. And so does the word incense derives from Latin incendere meaning ‘to burn. Perfume is a ‘mixture of fragrant essential oils or aroma compounds, fixatives and solvents’. Perfume and its evaporation process is metaphorically compared with music, as having three sets of notes rendered out in time. The Top note offers the introductory impression, such as mint, lavender and coriander. The head note arrives before the diffusion of the top note and masks the often unpleasant initial impression of the head note. These smells include seawater, sandalwood and jasmine. The base note, after nearly 30 minutes of the application brings in depth and solidity to the experience of a perfume. Examples of base notes include tobacco, amber and musk.

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Perfumes were used primarily by the wealthy to mask body odours resulting from infrequent bathing and lack of urinals in large estates (Versailles Palace) in 16th and 17th C. The smells were sought to be suppressed with cuttings of Orange trees. Fruits of citrus plants (Latin =Hesperidium), provide fresh, fleeting and effervescent fragrances. The Hesperides are nature nymphs in Greek mythology. By extension, the garden they tended also was known by that name. Other scents derive from: flowers, greens (freshly crumpled leaves, cut grasses), spices, foods and beverages, wood and mosses, resins and balsams and animal smells.

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Post 50 –by Gautam Shah

(Lecture series: Space Perception -Article-V of 15)


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Objects are sensed as physical things, hyper real recollections and mix of both. Collection of objects random or arranged, reflect relationships at many different levels. The basic relationship that we perceive is the degree of nearness or farness in time and space. These also define the forward-backward in spatial terms, and previous-later positions in time, of the objects. Other relationships that we perceive about objects include diversity and commonality, continuity and separation, complete figures and partly occluded articles, static and dynamic forms.

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The perception of objects occurs through all senses. Some senses, like vision and audio are capable of measuring objects and their distances. But sense of smell, taste or touch are only fuzzily indicative of location and direction, and so do not offer the spatial totality.

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Objects appear as recollections, but without any sequence or time reference. Objects appear as flitting images, without any clue of their relevance or origins. Such recollections seem to be individual ‘frames or shots’ of happenings, but without any distinctive links to the greater whole. The images do not have any concern with the past, present or future but are altered compositions, which perhaps our subconscious expects or desires. The recollections represent intense sensual experiences, but need definitive context, otherwise these can remain sporadic and unrelated incidences.

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The spatial and temporal contexts are the most important aspect of perceiving objects. Spatial context provides a ground for comparison of ‘scenes’. The comparison occurs in terms of size, scale, direction or orientation and nature of exposure to the ‘scene’ (forward, backward, partly occluded). Spatial context emerges from three references, the position of the perceiver, the adjacent objects and environmental effects. The temporal context relates to sequence of happening, duration, rate of change and chances occurrence.

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The spatial and temporal contexts are relevant mainly due to environmental effects. The effects are spatially directional and variable in time. And both of these factors continually create new compositions of objects. Environmental effects mould the experiences. Objects seem closer or far from each other. We tend to see complete figures or forms from sparing details, if we had past encounter with such objects. Similarly we build hyper real bridges of relations or connections between objects that are far distanced from each other, and often out of the scope of perception.

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Objects are marked by conditions that indicate direction. The direction indicators are experienced on objects that are long, short, sharp-edged or rounded, affected on few faces by the environment, and with graphics. The direction indicators in static objects represent potential for movement. Objects that have sequencing motifs such as forms that have overbearing pointers, retreating or advancing repeats, fading or intensifying clarity, varying environmental effects also state directions, and so movements.

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Directions and movements in groups of objects are perceived, when the real, hyper-real and remembrances, all have the same reference frame or datum. Here the reference frame is evident through the features remaining strong and consistent. Environmental effects are directional and so suggest the change when the real and remembered perceptions merge.

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Our perception of objects is always unequal. The unequal experiences help in exacting or blurring a location. The former (exacting a location) is due to the duality of the sensorial nodes like ears and eyes and the later (blurring) is due to synchronicity of two nodes like smell and taste or the widely placed multiple (like pain, temperature, moisture, etc.) tactile experiences over the entire body surface. The unequal perception is due to age, natural proficiencies and experience building exposures.

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One of the remarkable proficiency, natural or gained is about multitasking. Multitasking or multi attendance involves capacity to perceive many things concurrently, using the same or different sensorial nodes. Multitasking also may mean using various body limbs simultaneously.




Post 49 –by Gautam Shah

(Lecture series: Space Perception -Article-IV of 15)



Our experience of the world, is based substantially on the input of sensory information. It is a personal process. But we also learn from others about such experiences, accept it, or reconfirm that through our own encounters. It ultimately builds a large repertoire of experiences. We, are continuously exposed to several of stimuli, but remember or retain only few of them. We broadly distinguish our awareness about things and happenings around us, as focus or on margins. Perhaps, our repertoire of experiences helps to decide what is to be in focus and margin.


`Perception may be regarded as primarily the modification of anticipation’ (Art & Vision: E H Gombrich). We perceive objects and environment in space by selectively assessing or blocking the stimuli, in a process called cognition. It is mental acquisition of knowledge through the sensorial faculties. Human cognition is intuitive and conscious. It includes, remembering, forming associations, conceptualizing, and order recognition.


texting Touch screen

Perceptual organization occurs in many different ways, like:

  1. Things, if nearer, are perceived best.
  2. Things that have distinctive clarity due to environmental support are well perceived.
  3. Things that lie in the direction of the perception node are better sensed.
  4. Things that are in the foreground and not shrouded by other elements or effects, are easy to register.
  5. Things that have balance, symmetry, equality, pose as an extensive and comprehensive entity and so easy to recognize.
  6. Experiences that are within recognizable time and space segments seem of the same category.
  7. Objects and happenings are comparable as whole or in parts, have some similarities within the perceptual frame, or somewhere back in past experiences.
  8. Things that have continuous form (unbroken or interconnected sub-elements) and contrasting silhouettes (order that ties up several sub-elements) are easy to discern.
  9. Happenings that have distinctive and predictable order of change (directions, rise or depletion of the intensity, rhythm), can be sensed even in highly chaotic condition.
  10. Perception is comprehensive if different nodes of sensorial perception offer a confirming experience, or else doubts persist.

Eye Patches

We continuously shift our attention, even while both, the environment and its cognition manifest. There are several hypotheses to explain how and why we shift the attention. It is said that what we know and, what we expect the thing to be, attract the attention first. Some believe that we process our repertoire of experiences into the core and marginal. Others believe we assess and ignore the less wanted stimuli. These occur asdistributed processing’, at sensorial nodes, possibly at many intermediate places or central-mental level. The process possibly, occurs with individual sensorial faculties. But somehow the sensorial faculties supplement each other. Some type of auto regulation creates the equipoise.


Nominal five senses of perception relate more to the external stimuli. But organs in the muscles like tendons and joints indicate the position of body-limbs and state of tension in the muscles. Similarly ear fluids make us aware of the balance of the body. The process of supplementing the perception by sensorial faculties is subliminal, but one may learn it when a particular faculty is debilitated or occluded. Vision deficiency enhances the touch and hearing abilities. Taste is supplemented by smell.


Depth is a measure, perceived through vision, hearing and smell and touch-proximity. The presence of dual (two eyes-ears) or multi-nodal (touch) perceptions define the direction and make the depth measure more accurate. The movement of eyes and ability to focus creates a sense of visual and aural perspective. Here the far-off objects become duller and the intervening distances proportionately change.



The perception of depth with direction becomes precise with the context of environment. Visual perception includes shadows that tell us about the ‘other’ (concealed) facets of the objects, and direction of the Sun (and so orientation). It also shows the difference between natural and artificial sources of illumination. Effects of surface illumination are visually perceived as change in the tonal intensity and texture. The colour tone and texture, both are also perceived, even from a distance, through surface sensation of hot-cold.


Aural and smell perceptions also include variations in scales and directions. For aural perception, the echoes, reverberations, change of selective frequencies and transmission channels (ducts, corridors, dome), help to learn about the quality of space. Smell traces get mixed up with others and that shows their path, and mediating elements like air movements.

Coffee Shop

Hookah + Coffee Zone Istanbul Turkey 1900

Sensorial perceptions occur in many different types of context. The cognitive processes compound that information and also show how to further use it. The context is highly variable, offered by the moment to moment changes and relevant past experiences. The differing contexts provide measure for change, like the intensity, direction and probability. Sensorial perceptions mutually offer the context for any happening. We listen to some thing and turn our eyes to it, focus our eyes to see a detail, smell with deeper breadth, or use fingers, palms or cheeks to feel the temperature-pressure sensations (air, hot-cold).



The most important context is the perception of differentials in movements. Objects, sounds, smells, etc., that are nearer, or moving towards us, indicate rapid changes, but we may not feel the change if the setting is very familiar. Here a lot of pre information maintains perceptual constancy. In case of simultaneous changes across several sensorial perceptions, the cognition may be confused.




 Post 48 –by Gautam Shah  (Lecture series: Space Perception -Article-III of 15)


The Illumination in a space is fairly consistent due the fairly steady source and predictability of the change. As one moves around a spatial field, things are perceived from different positions and in different contextual conditions. Other important factor that leads to changed perception is the increasing maturity of cognition. With the duration and proximity we learn lot more about the spatial field.

Light Corridor Hallway Shadows People Aisle View

There are many ways the eyes move. “Our eyes converge as well as diverge” according to the intensity of light and size of the field to be scanned. The fovea region in the retina of the eyes helps in perception movement. In even seemingly non-moving eyes, small jiggling movements, called micro-saccades to occur. The broadest movements occur with gestural movement of eyes and heads and shifting during postures.

Light And Shade Corridor Light Building

A spatial field has many depths.

Some fields, closer to the position of perception are illuminated with sources under our own control. Here the illumination conditions can be changed at will, or the position of perception shifted around. In both of these cases, the cause-effect has some certainty.

Bistro Dining Tables Restaurant Local Inn Table

Fields that are faraway from the position of perception are illuminated with sources under no-one’s control. Here the illumination conditions cannot be altered at will. Shifting the position of perception perhaps changes the contextual conditions, but the illumination component of the scene remains nearly static.


In very vast natural scapes the contrasts (changes) due to illumination are not highly noticed except in variable cloud cover, or during sunlight refraction at morning-evening periods.A brilliant sunrise, sunset or cloud formation in illuminated distant sky, show very little effect on the perception foreground of landscape’.


The effects of illumination are more pronounced and under control in restrictive space fields such as the built-forms, interior spaces and neighbourhood extents. Here the changes in contextual conditions accompany the changes in the foreground or components of the scene, so both seem controlled and restrained.



A spatial field is illuminated by natural light as Direct sun light, Sky Component (SC), Reflected Component (RC) of natural light, artificial illumination, and in many urban areas from surroundings’ lights like a street and vehicles. In addition to these sources, we use fluorescence to aid perception.

Fluorescence and phosphorescence are form of luminescence, or the emission of light by a substance that has absorbed light or other electromagnetic radiation.


The illuminants’ contexts are: strength and direction of source, background and foreground brightness, reflectance from surroundings, colour of light, multiplicity of sources. Other conditions include variability of space, objects and presence of dynamic (moving-vibrating) elements.

Built Space forms are occupied by objects, people and environmental effects but these rarely occur distinctly alone, in any rational form or within a nominal framing reference. The illuminants complicate the scene even if these elements manifest in for a fraction of a moment or remain unvaried for a very long period.


Single source illuminants are very definitive but complications arise due to the reflectance from many surfaces, directions, strength (brightness) and colour. Such complications are compounded with increasing number of original illuminants. Single illuminant defines a space and its objects in familiar sense, but fail as soon as the position of perception changes. Single illuminant is an irritant if any part of space has flickering movement (eg. Fan, moving curtains). Single illuminants are ideal for ‘object modelling’ as the shapes emerge without any compromises.


Perception ambiguities and compromises occur when an object or a group of overlapping objects, are lit by nearly same tonal colour value as the background. Indistinct figure-ground contrast, dissolve the edges. We tend to relate larger elements as the ground, over which smaller entities exist.

The objects are seen composition of surfaces that reflect incident light. Besides the variations caused by the angular exposition of surfaces, the surface quality or textures are detected by naked eye (at 0.07 mm). Smaller scale variations affect the gloss of the surface and mirroring effect of the surface. Very large surfaces have possibly no edges or breaks, and so are perceived through local variations of illumination.



Spatial forms are recognized with illumination references such as the proportionate extent of foreground-background, framing, strength of silhouettes, partial occlusion of elements, shading with the differing contrast and direction of the shadows, and diffusion by way of reflection, and refractions.

Stainless Design Stainless Steel Steel Building

Illuminated forms become difficult to recognize when an object curves around out of sight. Such occluding contours dissolve the edge of an object, and present poor silhouette formation. The absence of a well-defined contour renders the surface shapes (such as convex/concave) ambiguous.


The process of perception is a two-way affair. Position of a person and relative source of illumination are very important consideration for Space Planning. A person trying to project own-self must be aware of the perceiver’s distance, angles of connection, social dependency and postural condition. A strong back illumination, makes it difficult to perceive a chair-person’s features and gestures.

Concert Instrument Bass Sound Music Guitar Rock

Position of a person relative to the source of illumination also holds true in conference rooms, executive cabins, reception areas, lecture rooms, press conference rooms, etc. Natural or artificial illumination -as singular source and that too from the backside must be avoided, and if inevitable, reinforce it with lighting from other directions. One of the simplest ways is to envision how the situation manifests from every single position.

The daytime happenings, change considerably at supper time, as the ‘backbite window’ illumination is replaced with artificial lighting. Nominally the situation should stand corrected (if not reversed), but attitudes formed during daytime persist at other times. Shops in business districts are low illuminated because the staff is occupying the space for longer time and so is accustomed to low level (or even to save power), but customer entering from bright outside finds the darkness discouraging.

Side illumination eliminates many of the anomalies of perception and recognition but not all. To create good diffusion, the source for side illumination needs some depth from the occupying position. In small rooms this is rather difficult and requires careful design.


We are more used to illumination from top. But very strong such sources create under the chin shadows. This can be corrected by illumination from other directions, or from floor and table top reflections. Light colour floors and table tops, needs to be excluded from TV camera shooting angles. This is done by positioning the participants on a raised platform, and cameras at a slightly lower level then the table tops.


This is the III article (of intended 15) in series ‘Space Perception‘ that will form a course of One semester.


SOME SOUND BITES -Space Perception -I

Post –46  by Gautam Shah (Lecture series: Space Perception -Article-I of 15)



Sound is caused by disturbance or vibration in an elastic material. That energy of vibration is perceived as a subjective experience by the human ear. Ears capture, transmit and transduce the sounds by discriminating the sounds of different frequencies, and perceiving the same in different manners.


Human ear can perceive sound above infra-sound 20 Hz, and below ultrasound 20000 Hz, but more importantly human ears can discern information from sound and noise. Range of Human voice is from 60 Hz to 10000 Hz, but 90 % intelligibility occurs 200 Hz to 4000 Hz.

NASA Orion acoustics test

A modern good quality PA system should be capable of 100 Hz to 6000 Hz and preferably 10000 Hz. For music the PA system should be 80 Hz to 10000 Hz and up to 15000 Hz for high quality theatre type of installation. Telephone voices have peculiar ‘unnatural’ feel because voice frequencies below 400 hertz and above 3,400 hertz are eliminated.


When machines are taught to speak like humans, the process of learning (AI) is to break human speech into phonemes (each of 30 micro seconds slots). This forms the basic set and used for enunciation, so when robots speak, they sound monotonic, stilted and mechanical.

Human speech consists of two parts: vowels and consonants. In general vowels are easily recognized because they are distinctive and especially the `deeper’ or the longer vowels occupy more time than any other speech component. They also consist mostly of lower speech frequencies. The formative characteristics of the mouth, based on the cavity resonance, are responsible for vowel sounds, and the main vehicle for the intelligibility of the speech.

Arnold_Lakhovsky_ConversationConsonants are less easy because they occupy a very short time and so seem transient. These mostly are of higher speech frequencies (1200 Hz). There are many more of them than vowels and so offer speech audibility and perception. Consonants provide the rich sound variants that make different speeches different.

BushIn addition to the formats, sibilants, it is a consonant, with characteristic hissing sound (such as sh, s, z, and zh), and stops of various types (consonant sounds such as b, p, d, t, g, k) are characterized by the momentary blocking of some part of the oral cavity, help in high intelligibility.


The sound perception and cognition system has the ability of compensating and filling in the required information in terms of vowels, consonants, and even words into speech or sentences. The time required to fill in the required information is provided by the quality of acoustics of the space.A longer reverberation seems to elongate the spoken sound in time scale, but an excess of reverberation may mask the following sounds. A fast orator in a reverberating hall fails to impress the audience, whereas a slow speaker in well absorbent and non reverberating space may seem discontinuous.’

Rousselots_Apparat_zur_Aufzeichnung_der_SpracheSpeech intelligibility depends on the quality of space. The space, size, shape, materials and the PA system (if any) define how the speech will be perceived. Seasoned speakers or stage performers (actors, singers) have innate sense on how to improvise the tonal quality of delivery. They overcome (masking) the effect of background noise by raise the voice and change the range of frequency. In spaces with longer reverberation the pauses are widened. Speakers face the section of crowd they want to address, to direct the original sound and allow them (section of crowd) to read the lips and body gestures.


Speakers (orators, actors and singers) and Listeners, all hear original sound as well as reflected sounds, but in completely different spatial context (space, size, shape, materials and the PA system). For listeners the most important matter is the identification (real or mythical) of the source of sound, in spite of the ‘presence of many reflected sounds’. This helps in personalization or being part of the event. However if the time gap between the hearing of original sound and reflected sound is more than two seconds, the localization begins to be difficult. In long or a deep hall the P.A. system sounds arrives stronger and even before the arrival of direct sound creating confusion including visual and aural synchronization of lip and other body posture-gesture language with the spoken sound.


In case of speech, a short sound reverberation time, implies high absorption, which makes, in the rear seats, a speech registration difficult. On the other hand, a long reverberation time means, the sound of each syllable is heard against the reverberant sound of previous syllables.


This is the I st article of the series on SPACE PERCEPTION